Why Rotation Pays Off on a Small Plot

Most allotments are a similar size, and every inch feels precious. The temptation is to plant wherever there's a gap, and for a season or two that works. Then the trouble starts: brassicas sulk and swell at the roots, onions come up with white rot, potato yields dip. Rotation is the cheapest fix you'll ever make.

Moving crops around on a predictable cycle disrupts pests and diseases that overwinter in the soil and specialise in one plant family. It also balances what each bed takes out and puts back. Hungry crops such as potatoes and courgettes strip nutrients; legumes add nitrogen; roots and salads need far less. Rotate properly and you're feeding the soil rather than chasing problems.

The Four Groups to Move Around

Everything you grow belongs to a plant family, and families are the unit that rotates. Group them into four and you have a workable cycle.

• Legumes — peas, broad beans, runner beans, French beans, plus field beans sown as green manure. Their root nodules fix nitrogen, leaving the bed richer than they found it.
• Brassicas — cabbage, kale, sprouts, broccoli, cauliflower, swede, turnip, radish and rocket. Hungry for nitrogen, fond of lime, and prone to clubroot.
• Roots and alliums — carrots, parsnips, beetroot, onions, garlic, leeks and shallots. Light feeders that resent fresh manure, which makes roots fork.
• Potatoes and friends — potatoes, tomatoes, peppers, aubergines and courgettes. Heavy feeders that love a muck-laden bed and whose sprawling haulms smother weeds.

A Four-Year Plan That Fits a Small Plot

Divide the growing area into four roughly equal beds — they needn't be identical, just consistent from year to year — and mark them A, B, C and D. Each season, every group moves one bed along.

In year one, bed A takes potatoes and the squash family, planted into ground you manured the previous autumn. Bed B holds peas and beans. Bed C takes brassicas, planted into ground limed in winter and firmed well. Bed D grows carrots, parsnips, beetroot, onions and leeks — no manure this year, just a little balanced feed if the soil is thin.

Next spring everything shifts: potatoes to B, legumes to C, brassicas to D, roots to A. Three more seasons and you're back where you started, having given each bed a four-year gap between one set of brassicas and the next. That gap is the whole point. Clubroot spores survive in soil for many years and onion white rot is even more stubborn; a four-year break won't cure a badly infected plot, but it stops the problem worsening and gives you a fighting chance.

Feeding and Liming Without Confusing Yourself

Attach the soil preparation to the bed, not to the crop. Two rules cover most of it.

Manure before the hungry crops. Spread well-rotted manure or garden compost on the bed due to take potatoes and courgettes, in autumn or early winter, and let the worms work it in. Never sow roots straight after fresh manure — forked carrots are almost always a nutrient problem, not a soil one.

Lime before the brassicas. Apply garden lime in winter to the bed that will hold cabbages and their relatives, following the rate on the packet and testing your soil pH if you can. Aim for around pH 6.5 to 7. Never lime and manure the same ground at the same time; they cancel each other out. If your soil is already alkaline, skip the lime and simply firm the ground by treading it before planting.

Perennials, Winter Crops and Awkward Customers

Rhubarb, asparagus, artichokes, soft fruit and most herbs don't move, so give them a permanent bed outside the rotation. Strawberries are best kept as a separate patch too, replaced every three years or so.

Winter cropping is where tidy plans fall apart, and that's fine. Overwintering onions and garlic belong in the root bed even though you'll lift them the following summer — just note where they were. Spring cabbage and sprouting broccoli sit in the brassica bed. If a bed is bare over winter, sow a green manure: field beans or grazing rye hold nutrients and structure and can be dug in come spring. Avoid mustard before brassicas, as it shares their pests.

Keeping Track Without Fuss

Rotation only works if you remember what grew where. A cheap notebook and a pencil plan drawn each spring is enough — sketch the four beds, list what's in them, date it. Photograph the plot in midsummer when everything is in leaf, and check back before ordering seeds in January. Ten minutes now saves a season of guesswork.

Don't over-engineer it. If a crop fails and you replant with something from the wrong group, note it and move on. The aim is a sensible pattern most of the time, not a perfect one — and a plot rotated roughly for five years will outgrow one planted by whim every spring.